1. Field
The present invention relates to a secondary lock assembly for a fifth wheel hitch.
2. Background Art
Fifth wheel hitches are well known in the field of towing trailers using a truck or tractor. FIGS. 1A through 1C depict an exemplary tractor and trailer hitch arrangement employing a fifth wheel hitch. Tractor 100 is affixed with a fifth wheel hitch 103 to rear of tractor frame 105. Fifth wheel hitch 103 includes a fifth wheel hitch assembly 10 pivotally mounted on mounting brackets 185 by means of a mounting pin 187 inserted through corresponding bores through the hitch plate 30 and the bracket 185. The underside of the fifth wheel hitch assembly 10 includes a bearing 188 which rests upon the curved top of the bracket 185. Fifth wheel hitch assembly 10 comprises hitch plate 30 which houses a locking mechanism underneath with slot 135 opening toward the aft end of fifth wheel assembly 10 for receiving a kingpin 111 from trailer 119 and terminating toward the forward side in a u-shaped throat area 21.
Kingpin 111 typically extends from a trailer bearing plate 107, which rests upon fifth wheel assembly 10, specifically, upon load area 145 of fifth wheel hitch plate 30. Kingpin is, typically, a unitarily constructed article comprised of a lower flange 115 capping a shank 113 which extends from collar 117.
One known form of fifth wheel coupling is disclosed in U.S. Pat. No. 6,352,277 in which a hitch plate provided with a slot for reception of a shank portion of a king-pin of a trailer, a pivotally mounted jaw member for holding the king-pin in the slot and a locking wedge for locking the jaw member in its closed position. The jaw member includes a forward arm extending in a different (lower) plane to a hook. The arm, in use, is contacted by the lower flange of a correctly aligned king-pin, and causes the jaw member to pivot so that the hook engages the shank of the king-pin. This assembly is tied to a pull bar through a pivotal connection to the locking wedge with a tie bar.